RESPONSE OF UNDERGROUND BIOMASS TO DIFFERENT GRAZING INTENSITIES IN THE Stipa breviflora DESERT STEPPE

After eight years grazing treatment,the underground biomass including dead and living biomass under different grazing intensities(i.e.non-grazing,light grazing,moderate grazing and heave grazing,simplified as CK,LG,MG and HG)were measured with the method of random field sampling and laboratory separation in Inner Mongolia Stipa breviflora desert steppe in May 2009.The relationship between underground biomass and grazing intensity was discussed.The results showed that grazing influenced the underground biomass obviously,and the underground biomass decreased with the increasing of stocking rate.The underground biomass were 965.6 g·m-2,874.0 g·m-2,701.9g·m-2 and 785.8 g·m-2 in CK,LG,MG and HG respectively.In which CK underground biomass was significantly higher than MG.The underground biomass in HG was higher than that in MG because of the increase of Artemisia frigida in HG.Living underground biomass proportion of MG was the highest,it occupied 19.49% of total underground biomass,and that was lowest in CK(12.86%).The underground biomass mainly distributed in 0–30cm top soil(more than 80%).The distribution pattern of the underground biomass was like a letter T.To some extent,the growth of vegetation roots was promoted by grazing.It meant that the underground biomass under grazing were higher than that in CK.